Bought a second hand 450 sm just attempted first oil change. Loosend of plug 1 which felt 'locked' up to start and then it just starts spining and trickling a tiny bit of oil. Cant get the thing off or tighten it up, have a bad feeing about this one as the oil screen bolt is also locked solid. Any ideas thoughts or help greatly appreciated. In North London any mechanics or dealers recomendations also appreciated.